(1) Field of the Invention
The present invention relates to a display device, and in particular to a display device having a front window.
(2) Description of the Related Art
Various types of display devices, such as liquid crystal modules (liquid crystal display devices) and organic electroluminescent display devices, have been used for many portable information devices, such as cellular phones, personal digital assistants (PDA's), digital cameras and multimedia players.
In recent years, such display devices have generally had a hybrid structure where a transparent protective cover is pasted as a front window in order to protect the display panel, as shown in JP 2010-237447A. In addition, multifunctional display devices have been provided with a touch panel (TP), as shown in FIG. 1, and thus a structure where a touch panel and a front window have been pasted in sequence to the display panel on the surface side has been proposed.
In the touch panel shown in FIG. 1, a flexible printed circuit 11 for wiring is connected to the capacitive touch panel glass 10, and furthermore, an electronic part 12 for controlling the operation of the touch panel is provided and an interface terminal portion 13 is formed at the other end of the flexible printed circuit if necessary.
Meanwhile, as shown in FIG. 2, the colored section 20 is printed on the rear surface of the front window (FW), excluding the image display region of the display panel. Particularly in the case of a liquid crystal display device, the section 20 is colored black so that light from the backlight does not leak from any other area than the image display region.
The colored section of the front windows, however, are directly looked at by the user, and therefore it has been required for the section to be of a color other than black in recent years. It is indispensible for the colored section other than black to be printed with a thicker layer in order to prevent light from leaking.
In the case where the section on the front window is printed with a color other than black, as shown in FIGS. 3 and 4, bubbles (voids in the adhesive film) easily form between the adhesive film 30 and the front window (A) or between the adhesive film 30 and the touch panel (TP) (B) in the vicinity of the colored section 20 when the front window (FW) is pasted to the touch panel (TP) or the display panel.